Data compression is used for reducing the cost of storing large data files on computers. It is also used for reducing the time of transmitting large data files between computers.
Certain techniques are good for compressing certain images, but not others. As an example, palettization provides good bit rates for lossless compression of images having only a small number of colors. However, the bit rates can be rather poor for images having large numbers of colors. In some instances palettization can increase file size, due to the cost of describing palettes.
As another example, a lossless compression technique such as JPEG-LS scans through image lines, adaptively changing according to local image statistics. However, the image statistics only take limited advantage of vertical spatial locality. In addition, bit rates are not fully exploited if portions of an image contain only a few dissimilar colors.
Moreover, compression techniques such as palettization and JPEG-LS do not compress image sequences any more efficiently than single images.